The present invention relates to a sheet feeding apparatus for a printing press, a punching machine or the like, for feeding sheets of paper one at a time from a stack of the sheets to a printing or punching unit, and more particularly to an automatic mechanism for loading a new stack of sheets.
A typical conventional paper sheet feeding apparatus comprises a main lift for elevating a pallet upon which is placed a stack of paper sheets to be fed to a printing press, a punching machine or the like. A sheet separator is installed over the stack of sheets which has been elevated to a predetermined position, to separate the uppermost sheet one by one. When the sheets of the stack have been fed considerably, a new stack of sheets must be loaded. In the known art, the loading of a new stack is carried out by manually inserting a plurality of parallel spits under the old stack of sheets, which has been consumed considerably, to support the old stack from below, and the main lift is lowered to receive the new stack of sheets thereon. The parallel spits are supported in cantilever fashion by an auxiliary lift.
The lowered main lift supporting the new stack of sheets thereon is then elevated until the uppermost sheet of the new stack is brought into abutment with the undersides of the spits. Thereafter, the spits are retracted so that the old stack which has been supported by the spits is placed on the new stack.
In the conventional paper sheet feeding apparatus described above, the spits extend and are advanced and retracted in the direction of feed of the sheets. When these spits are supporting the old stack, they deflect downwardly due to the load of the stack. It will be understood that the downward deflection of the spits is increased toward the tip ends thereof since the spits are supported by the auxiliary lift in cantilever fashion. This is undesirable because the stack of sheets supported by the spits are caused to have an upper surface inclined downwardly in the direction of feed of the sheets, as the surface extends from its position over the proximal ends of the spits to its position over the tip ends thereof, and because the sheet separator fixed at a predetermined position over the stack of sheets has different relative position relative to the uppermost sheet of the stack in the direction of feed the sheets. It will be apparent that this affects adversely to the sheet separating function of the sheet separator as well as to the sheet feeding operation, as will be described hereinafter in more detail, and that this necessitates readjustment of the position of the sheet separator as well as skill of the operator during the operation of the sheet feeding apparatus.
The present invention was made to solve the above and other problems encountered in the conventional sheet feeding apparatus and has for its object to provide an automatic sheet stack loading mechanism of a sheet feeding apparatus wherein the downward deflection of the stack of sheets does not adversely affect the sheet separating and feeding operation.